Oscillating piston pump for fluids

ABSTRACT

The invention relates to an oscillating piston pump for liquid and gaseous fluids, comprising: a pump housing having at least two sector-shaped working chambers, which are diametrically opposed relative to a pivot axis arranged in-between; an oscillating piston, having at least two displacement portions which extend diametrically relative to the pivot axis and are each received pivotably in one of the working chambers; an electric drive, which moves the oscillating piston alternately on a pivot movement between two turning points delimited within the working chambers; a group of outlet valves, which ensure the discharge of a volume displaced from the working chambers to a pump outlet; and a group of inlet valves, which ensure the entry of a volume flowing into the working chambers from a pump inlet. The group of outlet valves or inlet valves is arranged on both sides of each working chamber and communicates through the pump housing with the pump outlet or the pump inlet. The other group of inlet valves or outlet valves is arranged in the oscillating piston and communicates via a cavity in the oscillating piston with the pump inlet or the pump outlet.

The present invention relates to an electric swivel piston pump forliquid and gaseous fluids, which may be applied universally fordifferent applications, e. g., as an oil pump or as a compressor.

For this purpose, primarily revolving displacement pumps, for example,vane pumps or rotary vane pumps, are known in the related art, which arewidely used for liquid as well as gaseous fluids. During production, agreat number of components, such as vanes, springs and seals, must beinstalled at such vane pumps due to their configuration. Furthermore, inorder to ensure a long durability, numerous fits relevant for sliding orsealing must be manufactured with great dimensional accuracy at vanes,sliding slit pockets and the like, because occasional tolerancedeviations limit the functionality.

In addition, non-revolving displacement pumps with oscillating pumpcomponents, such as swivel piston pumps or pendulum piston pump, areknown from other applications, e.g. oil-free vacuum pumps, which areable to operate with gasses without a lubrication supply, the pistons ofthe pendulum running up against an air cushion at a stationary chamberwall. The pump assembly of such swivel piston pump may includerelatively few components, i.e., a piston capable of swinging or apendulum, and a pump chamber with valves, to be more precise.

The patent application DE 10 2016 119 985.0 of the same applicant, whichwas not yet published on the date of filing of the present patentapplication, describes a pendulum piston pump in an exemplaryapplication as an oil-free vacuum pump at a break booster of a vehicle.

This pendulum piston pump includes a pendulum, a pump housing, aplurality of check valves, intake ports and an eccentric drivingmechanism. The pendulum is pivotable around a pivot point and has twopistons. The pump housing has two sector-shaped pump chamber segmentsand lateral run-up surfaces that respectively limit outer-most positionsof the pivoting motion of the pendulum at each piston. Check valvesunblock a connection to the outside when receiving pressure from thepump chamber segments. Intake ports of the inlet are closed against thepump chamber segments during the pivoting motion of the pendulum due toan overlap with the respective piston. They are unblocked in a turningarea when passing through the outermost position of the piston. Aneccentric driving mechanism is provided between the pendulum and anelectric motor.

Such pendulum piston pumps or swivel piston pumps are relatively compactand powerful and have a simple assembly with few individual pumpcomponents. However, they are limited to the supply of gasses, i.e.,compressible mediums.

The object of the present invention is to provide another compact pumpwith an economic assembly that is also suitable for supplying fluids orliquid mediums.

This object is achieved according to the present invention with a swivelpiston pump having the features of claim 1 for liquid and gaseousfluids.

The electrically driven swivel piston pump comprising, among otherelements, a swivel piston having displacement sections which extenddiametrically and which are received in sector-shaped working chambersof a pump housing, as well as a set of inlet valves or outlet valvesarranged on both sides of the working chambers, is particularlycharacterized by the fact that the other set of the inlet valves oroutlet valves is disposed in the swivel piston and communicates with thepump inlet or the pump outlet via a cavity in the swivel piston.

The invention thus provides, for the first time, a swivel piston pump ofwhich the inlet guide or outlet guide opens into the working chamberthrough the pump housing on the one hand and through the swivel pistonon the other hand.

In conventional assemblies, in which the inlet guide as well as theoutlet guide open into the working chamber through the pump housing, anorifice, usually the one of the inlet guide, is covered by the pistonand only temporarily unblocked. A charge exchange with the workingchamber may thus only take place during a part of the piston stroke. Inorder to configure a volumetrically efficient operating path of thepiston effectively in favor of the displacement volume for each pistonstroke, a corresponding ability for charge exchange only extends to theturning area of the piston. Due to the short available time frame forfilling or taking in a pumping medium in an emptied working chamber,such swivel piston pumps or pendulum piston pumps are only suitable foran efficient operation with compressible, gaseous mediums.

By means of the assembly according to the present invention, the orificeof the inlet guide and the orifice of the outlet guide guarantee acontinual charge exchange across the entire piston stroke, which enablesa volumetrically efficient operation to be realized with incompressible,liquid mediums or a fluid with any arbitrary ratio of gas phase toliquid phase, in addition to compressible, gaseous mediums.

Compared with revolving displacement pumps, such as vane pumps, whichare suitable for supplying liquid mediums, the swivel piston pumpaccording to the present invention achieves an improvedperformance-dimension ratio.

In addition, the assembly of the swivel piston pump according to thepresent invention includes fewer components compared to vane pumps andfewer sliding contact surfaces, such that it may be produced moreeconomically with respect to assembly work and choice of materials.

Advantageous further embodiments of the swivel piston pump according tothe present invention are the object of the dependent claims.

According to an aspect of the invention, the cavity of the swivel pistonis opened towards an axial side relative to the pivot axis, and anorifice of the pump inlet or pump outlet facing the swivel piston may beformed in the pump housing so as to overlap an opening cross-section ofthe cavity.

Due to a corresponding end-face intersection of the inlet guide or theoutlet guide between the housing wall and the moved piston, a flowconnection may be realized by means of a gap seal or the like withoutinterfering with the piston motion. Compared to a flexible passage orthe like, a non-fatiguing flow connection is thus provided.

According to an aspect of the invention, the opening cross-section ofthe cavity may extend annularly around the pivot axis, and the orificeof the pump inlet or the pump outlet may be disposed centrally withrespect to the pivot axis.

This configuration achieves a regular flow cross-section at theintersection between the pump housing and the swivel piston across theentire pivoting motion.

According to an aspect of the invention, the cavity takes the form of ahollow space matching the outer contour of the swivel piston.

Due to this configuration, the flow cross-section is maximized in theswivel piston. At the same time, the oscillating mass of the swivelpiston and the necessary material usage is minimized, which lowers adrive power and material costs.

According to an aspect of the invention, the swivel piston may beproduced as a moulded plastic part having an overmoulded steel shaft asa pivot axis.

This choice of materials further favors the goals of a low, oscillatingmass as well as an economic implementation of the swivel piston as amolding piece.

According to an aspect of the invention, the outlet valves may be formedby flexible lock vanes that release an outlet side of a valve opening.

Due to this configuration, the valves of the pump are provided aseconomic bent sheet-metal parts or other flexible materials as a singlepart, which are, for example, punched out in the shape of a brace or thelike, formed, and inserted into a receptacle of the pump housing.

According to an aspect of the invention, the inlet valves are eachformed by an arrangement of prisms of triangular cross-section which areflexibly movable with respect to each other, said prisms being disposedfacing a flow direction with an apex edge of the cross-section and beingdisposed perpendicularly facing a shut-off direction with a lateral sideof the cross-section.

Due to this configuration, the valves of the pump are manufactured byselecting a material of suitable elasticity as a molded piece or evenintegrally with the molded piece of the swivel piston. Theflow-effective shape and alignment of such flexible, prismatic valveelements causes the same to automatically spread or press together as afunction of the flow-through direction. In the shown application asinlet valves at a swivel piston, the functionality of closing andopening is additionally, simultaneously supported by the mass inertia ofthe flexible valve elements in the oscillating acceleration progressionof the piston.

According to an aspect of the invention, the electric drive may beconfigured as a rotary solenoid drive, the armature of which may bepivoted electromagnetically around the pivot axis between two workingpoints, and is fixed non-rotatably with the swivel piston.

The drive concept of a rotary solenoid drive is ideal for the operatingmode of an oscillating displacement piston, because the generated andthe required torque progression are not constant but increase equallytowards the working points of the rotary solenoid or towards the turningpoints of the swivel piston.

In addition, a direct drive connection may be configured by means of ashaft without eccentric kinematics or the like. In addition, moreeconomic control electronics may be implemented as an ECU common in therelated art for a brushless dc motor.

According to an aspect of the invention, the electric drive may beconfigured as an electrically rotating motor that is coupled to theswivel piston via an eccentric actuator mechanism.

In the case of this alternative, an available variety of economicstandard drives may be used at least with respect to the electric motor.

The invention is described below in detail based on one exemplaryembodiment with reference to the drawings. They show:

FIG. 1 a cross-section through the swivel piston pump according to thepresent invention with a plan view of the swivel piston, the workingchambers and the valves;

FIG. 2 a perspective view of the swivel piston pump according to thepresent invention with a central intake port and a pressure socket;

FIG. 3 a longitudinal section through the swivel piston pump accordingto the present invention with a rotary solenoid drive.

First, the structure of an exemplary embodiment of the swivel pistonpump according to the present invention designed to be used as an oilpump in a low-pressure lubricant system, e.g., for supplying lubricationoil to gears in a transmission will be described with reference to FIG.1.

In FIG. 1, at the top left and lower right of a pivot axis 12, twosector-shaped working chambers 10 opposing each other diametrically areillustrated that extend inside the pump housing 1 on one plane with thepivoting motion of the swivel piston 2. The flanks of the workingchamber 10 form run-up surfaces for the swivel piston 2.

Illustrated at the top right and lower left of the pivot axis 12, twoareas of a pump outlet 14 connected via a bow-shaped channel in the pumphousing 1 are arranged between the working chambers 10. Between theworking chambers 10 and the pump outlet 14, valve openings are formed inthe run-up surfaces of the working chambers 10. The valve openings,together with clasp-like, flexible lock vanes 40 that respectively covera side lying on the outside with respect to the working chamber 10, ofthe valve opening, form outlet valves 4 of the swivel piston pump.

The swivel piston 2 is fixed on the pivot axis 12 which issimultaneously a drive shaft of the electric drive 3. The swivel piston2 includes two displacement sections 20 which are alternately pivoted inthe working chambers 10 over a rotational angle of approximately 90°, asshown by the double arrow. Between the displacement sections 20, theswivel piston 2 has a circular outer contour. The inside of the swivelpiston 2 is a hollow part and opened to the side of the viewer of theillustration, which results in a cavity 25. The cavity 25 surrounds anaccommodation of the pivot axis 12 and extends into the displacementsections 20.

Inlet valves 5 of the swivel piston pump are provided in the flanks ofthe displacement sections 20 that are pivoted towards the run-upsurfaces of the working chambers 10. The inlet valves 5 are formed byprismatic sections 50 and openings in the area of the wall of the swivelpiston 2 lying therein between. The prismatic sections 50 have atriangular cross-section and are formed integrally with the swivelpiston 2 at one end. Due to the fact that in the exemplary embodiment itis inlet valves 5 which allow a sucked-in delivery flow to pass throughfrom the cavity 25 into a working chamber 10 and which are supposed toblock in the reverse direction, all triangular cross-sections arearranged in a flow-efficient manner such that they point towards thecavity 25 with an apex and point towards the pump chamber 10 with asurface or hypotenuse of the triangle.

The prismatic sections 50 have a free end towards the open side of thecavity 25, such that they may incline at the free end like cantileversclamped in on one side when a material with sufficient elasticity ischosen, particularly a plastic material. When the pump medium flowsthrough, the prismatic sections 50 are thus flexibly inclined, eitherspreading apart at the free end or pressing together depending on theflow direction due to the different flow resistance of the triangularcross-section. A passage function and a blocking function thus result inopposing flow directions.

In the exemplary embodiment of the swivel piston pump, which isconfigured for use as a lubrication oil pump, that is, for pumpingmediums of higher viscosity, a sufficient valve function may already beachieved by means of the illustrated arrangement of three prismaticsections 50 with a central, larger cross-section, and two smallercross-sections offset thereto, the blocking function being improved byselecting different cross-section sizes.

In FIG. 2, an outer side of a pump cover 11 of the swivel piston pump isillustrated at which an intake port of the pump inlet 15 and a pressuresocket of the pump outlet 14 are apparent. The intake port of the pumpinlet 15 is arranged centrally with respect to the pivot axis 12 in thepump cover 11, such that it opens directly into the cavity 25 within thecircular outer contour of the swivel piston 2, independently of itsposition. As is apparent from FIGS. 1 and 2, the pressure socket of thepump outlet 14 opens into the area of the pump outlet 14 illustrated atthe lower left of the pivot axis 12.

As shown in FIG. 3, the pump housing 1 furthermore includes a flangesection, in which an electric drive 3 is accommodated, directed in thedirection of the working chamber 10. At a side of the pump housing 1shown on the right, another flange section closed by a cover 13 isprovided in which a control circuit 34 of the electric drive 3 isaccommodated. Lead terminals leading towards solenoids 30 of theelectric drive 3 exit from the pump housing 1 through a socketillustrated as being directed upwards.

In the shown embodiment, the electric drive 3 is provided by what iscalled a bistable rotary solenoid including two solenoids 30 and anarmature 32. The solenoids 30 are axially separated from one another andare in contact with two pole rings 31, which are also axially separated,and with a coaxial ferrite core 33. The armature 32 is pivotable on thepivot axis 12 and has two armature bodies which each have adiametrically longer extension of the circumference and, offset by 90°thereto, a diametrically shorter extension of the circumference, i.e.,for example, a circular area with two ring segments recessed at theinside opposite of one another. The armature bodies are eachaccommodated and mounted in a central recess of a pole ring 31. Eachrecess of the pole rings 31 has two opposing pole shoes.

When one of the solenoids 30 is supplied with current, the armature 32pivots into a position by means of a reluctance force, in which thecorresponding armature body aligns itself with its longer diametricextension between the pole shoes of the recess of the corresponding polering 31 in order to decrease the air gap and thus the magneticresistance in a magnetic circuit passing through the solenoid 30, theferrite core 33, the pole ring 31 and the armature body.

The pole shoes of the two pole rings 31 or the two armature bodies ofthe armature body 32 are off-set to one another by 90°. Thus analternating pivoting motion of the pivot axis 12 by 90° is generatedwhen the two solenoids 30 are alternately supplied with current by thecontrol circuit 34.

In the following, the functionality of the swivel piston pump will beexplained.

When the swivel piston 2 moves from the initial position shown in FIG. 1in a counterclockwise direction, a volume of the pumping medium isdisplaced in front of the swivel piston 2 or discharged from the workingchambers 10. The flexible lock vanes 40 of the outlet valves 4 arethereby pushed in an outward direction at the pressure side of theswivel piston 2 in the pump housing 1 and unblock the valve openings.The prismatic sections 50 of the inlet valves 5 at the front pressureside of the swivel piston 2 are press against one another at the freeends and block a passage to the cavity 25.

At the same time, negative pressure is generated in a section of theworking chamber 10 at the rear side of the swivel piston 2 such that avolume of the pumping medium sucked in through the pump inlet 15 followsand flows into the working chamber 10. Prismatic sections 50 of theinlet valves 5 at the rear intake side of the swivel piston 2 arethereby spread apart the the free ends by the delivery flow taken in andopen for a flow from the cavity 25 into the working chamber 10. Theflexible lock vanes 40 of the outlet valves 4 are pulled against thevalve openings in the pump housing 1 at the intake side of the swivelpiston 2 and block the outlet valves 4.

The same functionality is provided in a reverse pivoting motion back tothe initial position of the swivel piston 2 in FIG. 1. The swivel pistonpump is thus a double-stroke pump.

1. A swivel piston pump for liquid and gaseous fluids, comprising: apump housing having at least two sector-shaped working chambers opposingeach other diametrically with respect to a pivot axis positionedtherebetween; a swivel piston having at least two displacement sectionswhich extend diametrically with respect to the pivot axis and which areeach received in a swiveling manner in one of the working chambers; anelectrical drive which moves the swivel piston alternately between twoturning points on a pivoting motion contained within the workingchamber; a set of outlet valves which allow a volume displaced from theworking chambers to exit toward a pump outlet; and a set of inlet valveswhich allow a volume flowing into the working chambers to enter from apump inlet; wherein at least one of the set of outlet valves and set ofinlet valves) is arranged on both sides of each working chamber andcommunicates with one of the pump outlet or and pump inlet through thepump housing; and configured such that the other set of the inlet valvesor set of the outlet valves is disposed in the swivel piston andcommunicates with the pump inlet or pump outlet via a cavity in theswivel piston.
 2. The swivel piston pump according to claim 1, whereinthe cavity of the swivel piston is opened towards an axial side relativeto the pivot axis, and an orifice of the pump inlet or pump outletfacing the swivel piston is formed in the pump housing so as to overlapan opened cross-section of the cavity).
 3. The swivel piston pumpaccording to claim 1, wherein the opened cross-section of the cavityextends annularly around the pivot axis, and the orifice of the pumpinlet or pump outlet is disposed centrally with respect to the pivotaxis.
 4. The swivel piston pump according to claim 1, wherein the cavitytakes the form of a hollow space matching the outer contour of theswivel piston.
 5. The swivel piston pump according to claim 1, whereinthe swivel piston is produced as a molded plastic part having anovermolded steel shaft as the pivot axis.
 6. The swivel piston pumpaccording to claim 1, wherein the outlet valves are formed by flexiblelock vanes which release an outlet side of a valve opening.
 7. Theswivel piston pump according to claim 1, wherein the inlet valves areeach formed by an arrangement of prisms of triangular cross-sectionwhich are flexibly movable with respect to each other, said prisms beingdisposed with an apex edge of the cross-section facing a flow directionand being disposed perpendicularly facing a shut-off direction with alateral side of the cross-section.
 8. The swivel piston pump accordingto claim 1, wherein the electrical drive is configured as a rotarysolenoid drive having an armature which can be pivotedelectromagnetically around a pivot axis between two working points, andis fixed non-rotatably with the swivel piston.
 9. The swivel piston pumpaccording to claim 1 7, wherein the electrical drive is configured as anelectrically rotating motor that is coupled to the swivel piston via aneccentric actuator mechanism.
 10. A method of using a swivel piston pumpaccording to claim 1 for pumping liquid and/or gaseous fluids.
 11. Amethod of using a swivel piston pump according to claim 1 as alubricating oil pump for a transmission.